Biomedical subjects

Sebastian Wieczorek

Publications and source records attributed to Sebastian Wieczorek.

5 recordsLinked to original sources

PubMed2006

Self-induced chaos in a single-mode inversionless laser.

A single-mode inversionless laser with a three-level phaseonium as an active medium can by itself exhibit complex nonlinear dynamics. Nonlinear interaction between two spectrally separated gain regions of the phaseonium and a lasing field gives rise to instabilities and chaotic self-pulsations of a type not observed in conventional lasers with population-inverted gain media. We calculate the bifurcation diagram and uncover multistability and a torus-doubling cascade in transition to chaos.

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PubMed2004

Chaos in practically isolated microcavity lasers.

We report that essentially isolated microcavity lasers may interact in the most complicated manner and drive each other chaotic. As the optical isolation between these lasers reaches presently practically attainable limits, instead of approaching independent operation, the lasers exhibit mutually induced chaotic oscillations. The chaos arises from an intricate coupling of the nonlinearities associated with coupled optical resonators and those evolving from the population dynamics in the active region. The investigation is performed using a composite-cavity theory and a class-B description of the gain medium. Bifurcation analysis identifies the source of instabilities and determines their robustness.

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PubMed2004

Spontaneously excited pulses in an optically driven semiconductor laser.

In optically injected semiconductor lasers, intrinsic quantum noise alone, namely, the spontaneous emission and the shot noise, are capable of exciting intensity multipulses from a steady state operation. Noisy lasers exhibit self-pulsations in the locking region of the corresponding deterministic system. The interpulse time statistics are studied in parameter regions near k-homoclinic (Shilnikov) bifurcations where the corresponding deterministic model exhibits single-, double-, and triple-pulse excitability. These statistics differ significantly among each other, and they could be used to characterize regions of different multipulse excitability in a real laser device.

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PubMed2002

Global quantitative predictions of complex laser dynamics.

We demonstrate unprecedented agreement between a theoretical two-dimensional bifurcation diagram and the corresponding experimental stability map of an optically injected semiconductor laser over a large range of relevant injection parameter values. The bifurcation diagram encompasses both local and global bifurcations mapping out regions of regular, chaotic, and multistable behavior in considerable detail. This demonstrates the power of dynamical systems modeling for the quantitative prediction of nonlinear dynamics and chaos of semiconductor lasers.

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PubMed2002

Multipulse excitability in a semiconductor laser with optical injection.

An optically injected semiconductor laser can produce excitable multipulses. Homoclinic bifurcation curves confine experimentally accessible regions in parameter space where the laser emits a certain number of pulses after being triggered from its steady state by a single perturbation. This phenomenon is organized by a generic codimension-two homoclinic bifurcation and should also be observable in other systems.

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